WATER PURIFIER, ESPECIALLY FOR DOMESTIC USE

Abstract: A water purifier which works in accordance with the membrane distillation principle includes degassing means (7) for degassing incoming crude water prior to commencing the membrane distillation process; membrane means (16) for the membrane distillation of degassed water; and outlet means (20) which functions to discharge a residual quantity of degassed undistilled water when a degassed undistilled water level has fallen to a predetermined lower level in a container (3) which receives the crude water to be purified. The container (3) is provided with an upper level sensor (4) and a lower level sensor (18) and a temperature sensor (11). The upper level sensor (4) functions to activate the start of circulation means (5) for the circulation of crude water through the degassing means (7), and also to activate the start of crude water heating means (9). When the level of water in the container falls, the lower level sensor (18) functions to activate opening of the outlet means (20) so as to discharge remaining undistilled water. The temperature sensor (11) functions to cause circulation to the degassing means (7) to stop and to cause the circulation of degassed water to the membrane means (16) to commence for distillation of degassed water when a predetermined water temperature is reached.

Description: WATER PURIFIER. ESPECIALLY FOR DOMESTIC USE The present invention relates to a water purifier of the kind defined in the preamble of claim 1, and then particularly to a water purifier for domestic use. More specifically, the invention relates to a water purifier which purifies water by membrane distilla¬ tion. Membrane distillation per se is known to the art. For instance, European Patent Specification EP-O 118 760 teaches an arrangement for separating a volatile component from a solution, by pervaporation through vapour permeable membranes. These membranes are stretched in frames which separate different chambers one from the other. Crude water flows upwards in crude medium chambers at the same time as hot water flows down in heating chambers. Permeate is obtained in separate intermediate permeate chambers, by vaporiza- tion through the membranes. The German Patent Specification DE 3441190 also dis¬ closes pervaporation through membranes from crude medium chambers to permeate chambers, which are cooled with the aid of coolant on a side opposite the associated crude medium chamber. Although these and similar devices fulfil the purpose for which they are intended, they are not suited as a product for, e.g., domestic use, i.e. a use in which relatively small quantities of water are concerned and where purity demands and demands for very easy han¬ dling of the device are very high. The object of the present invention is to provide a water purifier of this kind. The inventive water purifier is defined in the charac¬ terizing clause of claim 1 and includes degassing means, membrane means and outlet means. The degassing means functions to degas incoming crude water prior to commencing membrane distillation. The membrane means functions to distill degassed water. The outlet means functions to empty remaining degassed, undistilled water when the level of degassed undistilled water has fallen to a predetermined lower level. According to a further development of the invention the water purifier includes a container for incoming crude water, wherein the container is provided with upper and lower level sensors and a temperature sen¬ sor, wherein when the crude water reaches an upper level in the container the upper level sensor func¬ tions to activate the start of circulation means for the circulation of crude water to the degassing means and also the start of crude water heating means, wherein when the falling water level reaches the lower water level in the container, the lower level sensor functions to activate opening of the outlet means so as to discharge the undistilled water that remains, and wherein when the temperature of the crude water reaches a given value, the temperature sensor func¬ tions to cause circulation to the degassing means to stop and to cause the circulation of degassed water to the membrane means, where distillation takes place, to begin. These and other characteristic features of an inven¬ tive water purifier are set forth in the following claims. The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawing, which illustrates an inventive water purifier schemat¬ ically and in perspective, with parts being cut away so that the construction can be more easily seen. The illustrated water purifier includes within a closed housing: - a fixed container 3 intended for incoming crude water and having fitted thereto an upper level sensor 4, a lower level sensor 18 and a temperature sensor 11; - degassing means 7; - fan means 10 mounted in the vicinity of the degas¬ sing means 7; - membrane means 16 fitted with air cooling means 161; - crude water circulating means 5; - crude water heating means 9; -outlet means 20 for discharging remaining quantities of degassed undistilled water and excess crude water and also possible products of degassification; and - two removable cans or bins 17 (only one of which is shown) for purified water. A brief description of the way in which the purifier functions, 1 - 4: 1. Filling Crude water is introduced into the purifier through an openable lid 1; the water runs past a waterseal 2 and a degassing tower 8 and down into the fixed container 3, which has a capacity of about 3.6 litres. 2. Degassing When the level of water in the fixed container 3 has risen to the level of the upper level sensor 4, the circulation means 5 (pump), the heating means 9 (im¬ mersion heater) and the fan means 10 are started-up. The crude water circulates through conduits 6 from the fixed container 3 to the degassing means 7 in the tower 8, where the water sprays out through a plurali¬ ty of holes 71 and forms a thin film on the walls of the tower 8. The water runs down, back to the container 3. Degassification products are sucked upwards by the upper fan means 10 and transported through a conduit (not shown) where condensation takes place, down to the outlet means 20. 3» PigtillatiQP The temperature sensor 11 senses the temperature of the crude water as it circulates. When the crude water reaches a temperature of about 98°C, a signal is sent to an electronic card 12 (processor) commanding the opening of a solenoid valve 13. The water is now degassed and shall be led - instead of to the degas¬ sing means 7 - to membrane cassettes in the membrane means 16 and from there through conduits 15 back to the fixed container 3 for heating. The hot water deliv¬ ers vapour to the cooling chamber via the cassette membranes, and the vapour condenses against cooling profiles, which are air cooled. Purified water runs down into the removable cans 17. 4. Emptying The level of water in the container 3 falls as distil¬ lation continues. When the water level reaches the lower level sensor 18, the sensor sends a signal to the processor 12 commanding a solenoid valve 19 to open the outlet means 20, whereby all remaining undis¬ tilled water (about 1.4 litres) is removed from the container 3. Emptying continues for about 5 minutes. The cans 17 now contain about two litres of purified water, produced in about one hour. After being emp- tied, the purifier can be refilled with crude water and the process repeated, automatically. If during the distillation process the temperature of the water should deviate from a given specific temper- ature, e.g a temperature of 98 β C, by a specific amount, e.g by 3°C, the temperature sensor 11 will send to the processor 12 a signal ordering the valve 13 to be closed, whereby degassing is restarted and the total amount of water remaining is heated before recommencing purification of the water through mem¬ brane distillation (the water will then have been heated to a temperature of 98°C). Expressed more generally, the aforesaid specified amount may be at maximum about 3% of the specified temperature. Because not all of the crude water taken into the purifier is distilled, it is possible that any con- taminants that have not been eliminated in the degas¬ sing process will remain in the volume of water that is left and the water may therefore contain an in¬ creased particle concentration when led away through the outlet 20. If crude water is introduced into the purifier through the intake at the lid 1 during the emptying process, this water will be led to the outlet 20 immediately and automatically. When crude water is purified in the described exempli- fying water purifier, the water entering the cans 17 will have a temperature of about 40°C. This water can be cooled to a temperature of 8-10 β C, by mounting a cooling loop in a known manner immediately upstream of the intake to the cans 17. The apparatus is also constructed so that if one of the cans 17 is removed during the distillation process (to use the purified water contained therein) that water which would otherwise be delivered to the can concerned is instead led directly to the outlet 20. Volatile substances present in the crude water are eliminated from the water after filling the container with about 3-4 litres of water, by virtue of the fact that the total amount of crude water is caused to circulate while being heated to a final temperature of 98 β C, e.g. at a rate of about 3-6 litres per minute, and is so pumped through the degassing tower that a thin film of water is formed on the inner surfaces of the tower. A suction channel provided in the tower communicates with a fan which sucks away undesirable substances continuously during the entire circulation and heating process, these substances having been released with water vapour and running out through the outlet. When the crude water has reached a temperature of 98°C, all volatile substances will have been elimi¬ nated. The process then passes automatically to the membrane distillation phase for the removal of solid particles and ions. In tests carried out on crude water containing 1000 μg THM (trihalomethanes) per litre of water, such as chloroform, bromoform, bromo-dichloromethane and dibromo-chloromethane, it was found that subsequent to removing the contaminants the amount of THM remaining in the water was less than 0.1 μg per litre of water, despite the fact that the boiling points of the major- ity of these contaminants were above 98°C. Thus, the inventive water purifier is effective in purifying crude water to a very high degree of purifi¬ cation, as mentioned earlier. The degree of purity achieved with the inventive purifier has been evaluat¬ ed in different test procedures carried out both before and after purifying the water. The following results were obtained: 1. Chlorine from 3.4 mg/1 to below 0.01 mg/1 2 Trihalomethanes from 1000 μg/1 to below 1 μg/1 3. Chloride from 31000 ppm to less than 1 ppm . Radioactivity 4.1 Strontium purification better than 99% 4.2 Radium purification better than 99.9% 4.3 Plutonium purification better than 99% 4.4 Cesium 134 from 2.4 + 0.2 Bq to 0 Bq 5. Bacteria after 2 days from 3800 to 0 after 7 days from 14000 to 0 It will be understood that the invention is not re¬ stricted to the illustrated and described embodiment thereof and that the invention can be implemented in any desired manner within the scope of the following claims.

Claims: CLAIMS 1. A water purifier, particularly for domestic use and functioning in accordance with membrane distilla- tion principles, characterized by degassing means (7) for degassing incoming crude water prior to commencing the membrane distillation process; membrane means (16) for the membrane distillation of degassed water; and outlet means (20) which function to discharge a resid- ual quantity of degassed undistilled water when a degassed undistilled water level has fallen to a predetermined lower level. 2. A water purifier according to Claim 1, character- ized by a container (3) for incoming crude water, wherein the container is provided with an upper level sensor (4) and a lower level sensor (18) and a temper¬ ature sensor (11), wherein when the crude water reach¬ es an upper level in the container (3) the upper level sensor (4) functions to activate the start of circu¬ lation means (5) for the circulation of crude water to the degassing means (7) and then back to the container (3) , and also to activate the start of crude water heating means (9), whereas when the falling water level reaches the lower water level in the contain¬ er^), the lower level sensor (18) functions to acti¬ vate opening of the outlet means (20) so as to dis¬ charge remaining undistilled water, and wherein when the temperature of the crude water reaches a deter- mined value, the temperature sensor (11) functions to cause circulation to the degassing means (7) to stop and to cause the circulation of degassed water to the membrane means (16) to commence for distillation of degassed water. 3. A water purifier according to Claim 2, character¬ ized by an upper fan (10) in the vicinity of the degassing means (7) for removing degassification products by suction and condensing said products during their transportation to the outlet means (20). 4. A water purifier according to Claim 2 or 3, characterized in that the temperature sensor (11) is intended to interrupt commenced membrane distillation when the temperature of the water deviates from a predetermined temperature by a given amount, and to start degassing and heating of the total amount of the remaining water prior to restarting the membrane distillation process. 5. A water purifier according to Claim 4, character¬ ized in that the temperature sensor (11) is intended to interrupt the membrane distillation process when the temperature deviation of the crude water reaches an amount which is at maximum 3% of the aforesaid predetermined temperature. 6. A water purifier according to any one of Claims 2 - 5, characterized by two readily removed purified water collecting vessels (17), wherein each of said vessels is intended to receive about half of the volume of water that is distilled when the container (3) is filled with crude water up to said upper crude water level. 7. A water purifier according to any one of Claims 1 - 6, characterized by air cooling means (161) for cooling the membrane means (16).

Inventors: SAEAESK AAPO, SYRJAELAE SEPPO, TELANDER FREDERIC, SAEAESK, AAPO, SYRJAELAE, SEPPO, TELANDER, FREDERIC
Applicants: HVR WATER PURIFICATION AB, SAEAESK AAPO, SYRJAELAE SEPPO, TELANDER FREDERIC, H.V.R. WATER PURIFICATION AB, SAEAESK, AAPO, SYRJAELAE, SEPPO, TELANDER, FREDERIC
Application year: 1994
Main classification: C02F1
IPC codes: B01D3, B01D61, C02F1, C02F103